a = float(input("Please input the a num : "))
if(90<=a<=100):
    print('A')
elif(80<=a<90):
    print('B')
elif(70<=a<80):
    print('C')
elif(60<=a<70):
    print('D')
elif(0<=a<60):
    print('E')
else:
    print('Score is error!')